JPH09294120A - Access control method and system for ciphered shared data - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow user groups to share data with security by using a ciphering communication technology. SOLUTION: A data ciphering section 14 and a data key ciphering section 15 of a terminal equipment 3 cipher data respectively by using a data key generated by a data key generating section 13 and use a public key 221 corresponding to a designated secrecy group to cipher the data key and a server 5 stores the data 211 and a data key 212. In the case of referencing the data 211, the terminal equipment 3 sends the acquired data key 212 and an open individual key 111 to the server 5, the server 5 uses a secret key to decode the data key 212 and uses the open individual key 111 to cipher the decoded data key and sends the result to the terminal equipment 3. A data key decoding section 17 uses a secret individual key 112 to decode the acquired data key and a data decoding section 18 decodes the data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an access control method for encrypted data, and more particularly to an access control method for sharing encrypted data among users having the same access right.

[0002]

2. Description of the Related Art As a method for cryptographic communication between a terminal device and a server device, for example, Japanese Patent Laid-Open No. 3-243035 discloses data encryption with a data key according to a common key cryptosystem, and a data key with a public key cryptosystem. Disclosed is an encryption communication system that encrypts and transmits by using the public key. Since the same data key is used for encryption and decryption of data, data encryption and decryption processing is performed at high speed.

FIG. 8 is a diagram showing the configuration of the encryption communication system. Each terminal device 90 has public private keys PP1, PP2, ... As many as the number of users and a secret key TS for each terminal.
Holds 1, TS2, ... The server 91 holds public keys TP1, TP2, ... Corresponding to terminals and secret private keys PS1, PS2 ,. The key management device 92 holds the public master key MP and the secret master key MS. The private private key is encrypted by the public master key MP. In the figure, the symbol X (Y) indicates that the object X is the key Y.
Indicates that it is encrypted by. The object X is data, a data key, a secret private key, or the like. When cryptographic communication is performed from the terminal device 90 to the user 1 who uses the server 91, the data key EK generated in the terminal device 90 is encrypted by the public private key PP1 of the user 1 and EK (P
The data key that has become P1) is transmitted to the server 91. Since the private private key PS1 (MP) is held in the area of the server 91 where only the user 1 has the access right, the user 1 accesses this private private key PS1 (MP), and the server 91 and the key management device 92. Data key EK (PP1) using the private private key PS1 after decrypting PS1 (MP)
Of the terminal device 90 using the obtained data key EK
The data DT (EK) sent from the server to the server 91 can be decrypted. When performing encrypted communication from the server 91 to the terminal device 90, the data key EK generated by the server 91
Is encrypted with the public key TP1 of the terminal and EK (TP
The data key of 1) is transmitted to the terminal device 90. In the terminal device 90, the data key EK (TP
The server 9 is decrypted by decrypting 1) and using the obtained data key EK.
The data DT (EK) sent from the terminal 1 to the terminal device 90 can be decoded. The key management device 92 encrypts the private private key PS with the public master key MP that cannot be read from the outside, and decrypts the private private key PS (MP) with the private master key MS.

[0004]

Although the above-mentioned conventional technology enables the secure registration and reference of data by using the cryptographic communication technology, the cryptographic communication is limited to the person-to-person communication, and the same data is used. There is no idea of sharing data between user groups that have reference rights. On the other hand, a technique called mandatory access control is known as a technique for sharing data that requires confidentiality, but this technique requires control by a special operating system. Otherwise it was not available. There is a demand for a technology for sharing confidential data between user groups by using highly secure cryptographic communication technology without introducing special hardware or operating system.

An object of the present invention is to provide an access control method for securely sharing encrypted data among user groups.

[0006]

SUMMARY OF THE INVENTION The present invention is an access control method for a system in which a plurality of terminal devices and a server device are connected by a network, and a public private key and a corresponding private private key are provided on the terminal device side. And holds the public department key and the corresponding secret department key corresponding to each level of security classification on the server side. The terminal device encrypts the data according to the common key cryptosystem, encrypts the data key using the public department key corresponding to the designated confidentiality category, and sends the encrypted data and the data key to the server, Stored in the storage device. When accessing the shared data stored in the server, the terminal device acquires the data and the data key from the server, sends the public private key and the received data key to the server, and the server uses the secret department key to transfer the data. Decrypt the key, encrypt the data key decrypted using the public private key and send it to the terminal device,
The terminal device decrypts the data key by using the secret private key, and decrypts the acquired data by the decrypted data key.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of an access control system of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of the system of this embodiment. The terminal device 3 is a device that inputs and outputs data. The server 5 is a device that stores the input data and data key, and also stores the department key (domain key) according to the confidentiality of the data. The key management device 8 is a device that stores a master key for decrypting the department key and decrypts the department key with the secret master key. In this embodiment,
A common key cryptosystem using the same key is applied to both data encryption / decryption. In addition, public key cryptosystems that use different keys are applied to the encryption / decryption of the data key that is the key when encrypting the data.

The storage device 11 connected to the terminal device 3 is
A public private key 111 and a private private key 112 are stored as private keys. The input / output unit 12 is a control unit that controls input / output of data from an input / output device such as a keyboard / display device / storage device (not shown). The data key generation unit 13 is a processing unit that generates a data key according to the common key cryptosystem. The data encryption unit 14 is a processing unit that encrypts the data input according to the common key cryptosystem with the generated data key. The data key encryption unit 15 is a processing unit that encrypts the data key generated according to the public key encryption method with the public department key 221. Private key access unit 16
Is a control unit that controls access to the private key of the storage device 11. The data key decryption unit 17 converts the data key received from the server 5 according to the public key cryptosystem into the secret private key 11
2 is a processing unit for decoding. Data decoding unit 18
Is a processing unit that decrypts data with a data key decrypted according to the common key cryptosystem. The communication control unit 19
It is a control unit that controls to transmit and receive the public department key 221, the data 211, the data key 212, and the public personal key 111 between the terminal device 3 and the server 5 via the network. In addition to this, the terminal device 3 has a processing unit for generating a private key.

The storage device 21 connected to the server 5 stores data 211 and a data key 212. Data 21
1 is stored in a state encrypted by the data key EK according to the common key cryptosystem, and the data key 212 is stored in a state encrypted by the public department key 221 according to the public key cryptosystem. The storage device 22 also stores a public department key 221 and a secret department key 222 as department keys. The secret department key 222 is the public master key 7 according to the public key cryptosystem.
It is stored in the encrypted state at 11. The reference / registration right table 23 is for registering the security classification level at the time of data reference and data registration for each user group, and is stored in the storage device connected to the server 5. The data and data key access unit 24 includes the storage device 2
1 is a control unit that controls access to the data 211 and the data key 212 on the first computer. The department key access unit 26 is a control unit that controls access to the department key on the storage device 22. The reference / registration right determination unit 25 is a processing unit that refers to the reference / registration right table 23 and determines whether or not the data reference and registration requested by each user are valid. Communication control unit 27
Controls the communication with the terminal device 3 via the network, and also communicates with the key management device 8 via the network with the public private key 111, the data key and the secret department key 222.
Is a control unit that controls to send and receive. Server 5
There are two modes: a mode in which a normal service is provided to a user who uses the terminal device 3, and a maintenance mode in which the normal service is stopped and the department key on the storage device 22 of the server 5 is updated. When the server 5 is in the maintenance mode, the processing unit for updating the department key (not shown) operates and updates the department key according to the data input from the input / output unit (not shown).

Storage device 71 connected to the key management device 8
Stores a public master key 711 and a secret master key 712 as master keys. The master key access unit 72 is a control unit that controls access to the master key on the storage device 71. The secret division key decryption unit 73 is a processing unit that decrypts the secret division key 222 with the secret master key 712 according to the public key cryptosystem and decrypts the data key 212 with the decrypted secret division key. The data key encryption unit 74 is a processing unit that encrypts the decrypted data key with the public private key 111. The communication control unit 75 is a control unit that controls communication with the communication control unit 27 via the network.
The key management device 8 has two modes: a mode for providing a normal service and a maintenance mode for updating the master key on the storage device 71, but the server 5 and the key management device 8 are in the same mode at the same time. Must. When the key management device 8 is in the maintenance mode, a processing unit that updates a master key (not shown) operates and updates the master key according to data input from an input / output unit (not shown) in the key management device 8.

The terminal device 3, the server 5 and the key management device 8
Is an information processing device such as a personal computer, and each control unit and processing unit is realized by hardware or by executing a program stored in a storage device of the information processing device.

FIG. 2 is a flow chart showing the flow of processing of the terminal device 3 and the server 5 until the data is encrypted with the data key and the encrypted data and the data key are stored in the storage device 21. Input / output unit 12 of terminal device 3
Inputs the aggregated data such as a file and its confidential classification (step 31). Data key generator 1
3 generates the data key EK (step 32). The data key is generated from this using seed data such as random numbers and dates. Next, the data encryption unit 14 encrypts the input data with the generated data key (step 33).
Next, the data key encryption unit 15 transmits a public department key transmission request to the server 5 via the communication control unit 19 (step 34). This transmission request includes the designation of security classification.
The communication control unit 27 of the server 5 receives this request (step 51), authenticates the user, and then the reference / registration right determination unit 25 refers to the reference / registration right table 23 to register the requested data. Is determined (step 5)
2). If the request is valid, the public department key 221 corresponding to the designated security category is retrieved via the department key access unit 26 and transmitted to the terminal device 3 (step 53). The data key encryption unit 15 receives this public department key 221 via the communication control unit 19 (step 35), and the data key E
K is encrypted with this public department key 221 (step 36). Next, the data encryption unit 14 and the data key encryption unit 15 send the encrypted data DT (EK) and the encrypted data key EK (DP), respectively, to the communication control unit 19
To the server 5 via (step 37). The communication control unit 27 receives the data and the data key, and transmits the data 2 via the data and data key access unit 24, respectively.
11 and the data key 212 are stored in the storage device 21 in association with each other (step 54).

FIGS. 3a and 3b are flow charts showing the processing flow of the terminal device 3, the server 5 and the key management device 8 when referring to the data stored in the server 5.
The input / output unit 12 of the terminal device 3 inputs the name of the target data, for example, the file name, and transmits a data request to the server 5 via the communication control unit 19 (step 41).
The communication control unit 27 of the server 5 receives this request (step 61), authenticates the user, and then the reference / registration right determination unit 25 refers to the reference / registration right table 23 to check the requested data. Determine if the reference is valid (step 6)
2). If the request is valid, the data key access unit 24
Is the data key 212 corresponding to the specified data 211.
And are transmitted (step 63). The input / output unit 12 receives the data 211 and the data key 212 (step 4
2), the public private key 111 via the private key access unit 16
Is taken out (step 43), and the public private key 111 and the received data key 212 are transmitted to the server 5 via the communication control unit 19 (step 44). The communication control unit 27 receives the public private key 111 and the data key 212 (step 64), and the department key access unit 26 receives the secret department key 22.
2 is taken out (step 65), and the public private key 111 and the data key 212 received from the terminal device 3 and the secret department key 222 taken out are transmitted to the key management device 8 via the communication control unit 27 (step 66). The secret division key decryption unit 73 of the key management device 8 receives these pieces of information via the communication control unit 75 (step 81), retrieves the secret master key 712 via the master key access unit 72 (step 82), The secret department key 222 with the secret master key 712
(Step 83), and the decrypted private sector key DS
Then, the data key 212 is decrypted (step 84). Next, the data key encryption unit 74 encrypts the data key EK obtained by the public private key 111 (step 85), and the data key EK (PP) is sent to the server 5 via the communication control unit 75.
Is transmitted (step 86). The communication control unit 27 receives this data key (step 67) and transfers it to the terminal device 3 (step 68). Data key decryption unit 17 of terminal device 3
Receives the data key EK (PP) via the communication control unit 19.
(Step 45), the private key 112 is retrieved via the private key access unit 16 (step 46), and the data key EK (PP) is decrypted by the private key 112 (step 47). Next, the data decryption unit 18 decrypts the previously received data 211 with the obtained data key EK (step 48), and the input / output unit 12 outputs the decrypted data to the output device (step 49).

FIG. 4 is a diagram for explaining the relationship between the data 211, the data key 212 and the security classification. The security classification is classified as level 1, level 2, ... Each level of security classification is associated with a group of users as described later, and each user group can use only the department key of the level registered in the reference / registration right table 23. Data 211 encrypted by the data key
Is independent of the classification. Since the public department key 221 and the secret department key 222 are set corresponding to the level of confidentiality, the data key 21 encrypted by the public department key 221 and decrypted by the secret department key 222.
2 is registered corresponding to any level of security classification.

FIG. 5 is a diagram for explaining an example of user authentication processing performed prior to data reference or registration. The server 5 holds the correspondence table of the user name and password of each user, the public key for authentication, and the private key for authentication in the storage device. The terminal device 3 is the entered user name (user code)
Is transmitted to the server 5. The authentication processing unit (not shown) of the server 5 refers to this table and, if the user name is registered, transmits the authentication public key IP to the terminal device 3. The terminal device 3 encrypts the entered password with this authentication public key and sends it to the server 5. The server 5 decrypts the encrypted password PWA (IP) with the authentication secret key IS to obtain the password PWA, and compares it with the password PWA corresponding to the user name A on the table. If the passwords match, the server 5 sends a message permitting the operation to the terminal device 3, and the terminal device 3 sends a request for data reference or registration. It should be noted that the authentication public key and the authentication private key are changed to new keys at an appropriate frequency.

FIG. 6 is a diagram for explaining a specific example of the process of determining the reference right and the registration right of the data, which is performed by the reference / registration right judgment unit 25. The user name / password correspondence table used for user authentication processing holds, for each user, the identifier of the user group to which the user belongs.
Further, the reference / registration right table 23 sets, for each group, a level of confidentiality class that allows data reference and a level of confidentiality class that allows data registration. A user who has the data registration right can also update the data. For example, since the user with the user name A belongs to the user group G1, he / she can only refer to the data whose security classification is level 1.
Moreover, only the data whose security classification is Level 1 can be registered. In addition, when changing the security classification of the data key, the user needs a reference right to the data before the change and a registration right to the data after the change. For example, when changing the security classification from level 1 to level 2, it is necessary to have a reference right to the data of the level 1 and a registration right to the data of the level 2 like a user belonging to the group Gp. In the example of FIG. 6, the security level n is
Set the authority to transfer data to other systems. Therefore, only a user who has a registration right for the data of level n, such as a user belonging to the group Gk, can transfer the data to another system.

According to the above-described embodiment, the data key 212 stored in the server 5 is encrypted corresponding to the security classification and the reference / registration right table 23 is checked to check the reference / registration right. Only users who have the reference / registration right with respect to the classified data can reference / register the data. Especially, in order to prevent the data of high confidentiality level from being rewritten with the data of low confidentiality level, the level of the confidentiality classification of the reference / registration right table 23 is set according to the degree of confidentiality, You can increase the security of sensitive data by limiting the level of classification that you allow. Further, since the user belongs to any of the user groups, it is possible to share the data having the classified classification permitted for the user group. The data key 212 corresponds to the security classification, but since the data 211 is independent of the security classification, the data key EK (D (D) does not need to be transmitted or decrypted via the network.
It is possible to change the security classification of P). After the data key 212 is decrypted in step 84, the data key EK
Will be independent of classified categories. Then, in step 85, the data is encrypted with the public private key and transmitted to the terminal device 3 via the network. Therefore, eavesdropping on the data key EK during network transmission is substantially invalid. Further, the administrator of the server 5 cannot decrypt the secret master key 222, and therefore cannot decrypt the data key 212, and thus cannot access the data 211 substantially. Furthermore, since the present invention can be realized at the application program level without depending on the operating system, access control that does not depend on specific hardware or operating system is possible.

FIG. 7 is a diagram showing an example of a system configuration to which the present invention is applied. The system A and the system B are composed of terminal devices 3 and 3 ', servers 5 and 5', and key management devices 8 and 8 ', respectively, and the system A and the system B are connected via a communication network.

By providing the public department key 221 and the secret department key 222 as a pair for each security classification, the data key 212 plays the role of security classification, and between the user groups who have the access right to the data of the security classification. You can share data with. Further, the public department key 221 of the data key EK1 (DP1) corresponding to the data DT1 (EK1) is set to D
When changing to P2, the terminal device 3 transmits the original data key 212 and the changed confidentiality category to the server 5, and the server 5 secret key DS1 (MP), data key EK1 (D
P1) and the public department key DP2 are transmitted to the key management device 8,
The key management device 8 uses the secret master key MS to generate the secret department key D.
DS1 is obtained by decoding S1 (MP). Next, after using DS1 to decrypt the data key EK1 (DP1) to form EK1,
The data key EK1 is re-encrypted with the new public department key DP2 to obtain the data key EK1 (DP2). The server 5 receiving this receives the data key EK stored in the storage device 21.
1 (DP1) is updated by the data key EK1 (DP2). As a result, the security classification of the data can be changed without decrypting the data DT1 (EK1). Similarly, when data is transmitted from the system A to the system B, the same procedure as above is executed for the data key EK1 (DP1), and the data is re-encrypted by the public department key DP1 ′ of the other system B to safely secure the other system B. Data can be transmitted to.

As described above, data reference and registration,
When changing the security classification of data or transmitting data to other systems, the server 5 always intervenes to authenticate the user and check the authority of data operation, so that unauthorized persons may illegally acquire the data. It is possible to prevent the operation of distributing data without permission. Further, even if the data and the data key transmitted from the server 5 to the terminal device 3 are tapped, the data key is encrypted by the public department key or the public private key, so if the private department key or the private private key is unknown, the data key is decrypted. It is understood that this is not possible and therefore the confidentiality of the data can be ensured.

Although the key management device 8 is provided as a device independent of the server 5 in the above embodiment, the storage device 21, the storage device 22, the data / data key access unit 24, the reference / registration right determination on the server 5 side. Unit 25, department key access unit 26, storage device 71 of key management device 8, master key access unit 72, secret department key decryption unit 73, data key encryption unit 7
Each processing unit and data unit of the key management device 8 may be provided in the server as long as 4 is maintained in an independent relationship. If the administrator of the server 5 is trusted, the master department key may not be provided and the secret division key DS may not be encrypted. Further, in the above embodiment, one key management device 8 and one master key are provided for one server 5, but it is also possible to provide a plurality of master keys for each of the plurality of servers 5 and the key management device 8. Is. It is also possible to provide one key management device 8 for a plurality of servers 5. Further, the user authentication method shown in the present embodiment is just an example, and other personal authentication techniques such as Kerberos authentication can be used.

[0023]

As described above, according to the present invention, it is possible to securely share data between user groups by using the cryptographic communication technique and realize access control that does not depend on special hardware or operating system. .

[Brief description of drawings]

FIG. 1 is a configuration diagram of an access control system according to an embodiment.

FIG. 2 is a flowchart showing a processing flow of the terminal device 3 and the server 5 at the time of data registration according to the embodiment.

FIG. 3a is a flowchart showing a processing flow of the terminal device 3 and the server 5 when referring to data according to the embodiment.

FIG. 3b is a flowchart showing a processing flow of the key management device 8 at the time of referring to data in the embodiment.

FIG. 4 is a diagram illustrating a relationship among data, a data key, and a security classification.

FIG. 5 is a diagram illustrating an example of user authentication processing.

FIG. 6 is a diagram illustrating a process of determining a data reference right and a registration right according to the embodiment.

FIG. 7 is a diagram showing an example of a system configuration to which the present invention is applied.

FIG. 8 is a diagram showing a configuration of a conventional cryptographic communication system.

[Explanation of symbols]

3: terminal device, 5: server, 8: key management device, 13: data key generation unit, 14: data encryption unit, 15: data key encryption unit, 17: data key decryption unit, 18: data decryption unit, 23: Reference / Registration Right Table, 25: Reference / Registration Right Judgment Unit, 73: Secret Department Key Decryption Unit, 74: Data Key Encryption Unit, 111: Public Private Key, 112: Secret Private Key, 21
1: data, 212: data key, 221: public department key,
222: private department key, 711: public master key, 712:
Secret master key

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Takaragi 1099, Ozenji, Aso-ku, Kawasaki-shi, Kanagawa Inside Hitachi Systems Development Laboratory, Ltd. No. Stock Company Hitachi Ltd. Public Information Division

Claims (5)

[Claims] 1. A plurality of terminal devices holding a public private key and a corresponding private private key, and a server holding a public department key and a private department key respectively corresponding to each level of confidentiality classification. An access control method for a system connected by a network, wherein a terminal device generates a data key, the data key is used to encrypt the data, and the public department key corresponding to a designated confidentiality category is used to the data. The key is encrypted, the encrypted data and the data key are transmitted to the server, the server stores the data and the data key in the storage device as shared data, and the terminal device stores the data from the server. The data key is acquired, the public private key and the received data key are transmitted to the server, the server decrypts the data key using the secret division key, and the public key Encrypting a data key decrypted using a private key and transmitting it to the terminal device, decrypting the data key using the secret private key by the terminal device, and decrypting the data acquired by the decrypted data key An access control method for encrypted shared data, characterized by: 2. Before the terminal device acquires the data and the data key, the server refers to the data from a user group to which the user belongs and a confidentiality category of data reference permitted to the user group. The access control method for encrypted shared data according to claim 1, wherein the presence or absence of authority is determined. 3. The terminal device further obtains the data key from the server, transmits the received data key and the changed security classification to the server, and receives the data key by the server using the secret division key. The data key is decrypted, the data key decrypted by the public department key corresponding to the specified confidentiality category is encrypted, and the original data key stored in the storage device is encrypted by the changed encrypted data key. The method for controlling access to encrypted shared data according to claim 1, wherein the method is updated. 4. A plurality of terminal devices holding a public private key and a corresponding private private key, and a server holding a public department key and a private department key respectively corresponding to each level of confidentiality classification. An access control method for a system connected by a network, wherein a data key is generated by a terminal device, data is encrypted using the data key, and the data key is used by using a public department key corresponding to a designated confidentiality category. Is encrypted, and the encrypted data and the data key are transmitted to the server, the server stores the data and the data key as shared data in a storage device, and the terminal device transmits the data and the data key from the server. The data key is obtained, the public private key and the received data key are transmitted to the server, and the key management device connected to the server uses the secret department key to generate the data key. Data key, and the data key decrypted using the public private key is encrypted and transmitted to the terminal device via the server, and the data key is decrypted by the terminal device using the private private key. An access control method for encrypted shared data, characterized in that the data obtained by the decrypted data key is decrypted. 5. A plurality of terminal devices holding a public private key and a corresponding private private key, and a server holding a public department key and a private department key respectively corresponding to each level of confidentiality classification. An access control system connected by a network, wherein the terminal device generates a data key, encrypts the data using the data key, and uses the public department key corresponding to a designated confidentiality classification to use the data key. Means for transmitting the encrypted data and the data key to the server, acquiring the data and the data key from the server, and transmitting the public private key and the received data key to the server And a means for storing the data and the data key in the storage device as shared data, and the server for decrypting the data key using the secret department key to obtain the public private key. Use Means for encrypting the data key and transmitting it to the terminal device, the terminal device further decrypts the data key received using the secret private key, and the data obtained by the decrypted data key. An access control system for encrypted shared data, characterized by having a means for decrypting.